Search Publications
Anomalous expansion of coronal mass ejections during solar cycle 24 and its space weather implications
Gopalswamy, Nat; Akiyama, Sachiko; Yashiro, Seiji +3 more
The familiar correlation between the speed and angular width of coronal mass ejections (CMEs) is also found in solar cycle 24, but the regression line has a larger slope: for a given CME speed, cycle 24 CMEs are significantly wider than those in cycle 23. The slope change indicates a significant change in the physical state of the heliosphere, due…
Unexpected variability of Martian hydrogen escape
Montmessin, Franck; Bertaux, Jean-Loup; Chaffin, Michael S. +3 more
Mars today is much drier than the Earth, though they likely began with similar relative amounts of water. One potential cause for this discrepancy is hydrogen loss to space, which may have removed a large fraction of Mars' initial water. Here we demonstrate an order-of-magnitude change in the Martian hydrogen escape rate in 2007, inconsistent with…
The bathymetry of a Titan sea
Paillou, Philippe; Zebker, Howard; Lunine, Jonathan +9 more
We construct the depth profile—the bathymetry—of Titan's large sea Ligeia Mare from Cassini RADAR data collected during the 23 May 2013 (T91) nadir-looking altimetry flyby. We find the greatest depth to be about 160 m and a seabed slope that is gentler toward the northern shore, consistent with previously imaged shoreline morphologies. Low radio s…
A rapid decrease of the hydrogen corona of Mars
Quemerais, E.; Bertaux, J. -L.; Chaufray, J. -Y. +4 more
Mars is believed to have lost much of its surface water 3.5 billion years ago, but the amounts that escaped into space and remain frozen in the crust today are not well known. Hydrogen atoms in the extended martian atmosphere, some of which escape the planet's gravity, can be imaged through scattered solar UV radiation. Hubble Space Telescope (HST…
Propagation of lower-band whistler-mode waves in the outer Van Allen belt: Systematic analysis of 11 years of multi-component data from the Cluster spacecraft
Santolík, Ondřej; Cornilleau-Wehrlin, Nicole; Kolmašová, Ivana +2 more
Lower-band whistler-mode emissions can influence the dynamics of the outer Van Allen radiation belts. We use 11 years of measurements of the STAFF-SA instruments onboard the four Cluster spacecraft to systematically build maps of wave propagation parameters as a function of position. We determine probability distributions of wave vector angle weig…
Wave activities in separatrix regions of magnetic reconnection
Fujimoto, Keizo
Two-dimensional particle-in-cell simulations have reproduced the waves consistent with those observed frequently in the separatrix regions of magnetic reconnection in the Earth's magnetotail. The key process generating the waves is intense parallel acceleration of the electrons due to an electrostatic potential hump formed in the inflow side of th…
First observation of rising-tone magnetosonic waves
Santolík, O.; Chen, L.; Cao, J. B. +7 more
Magnetosonic (MS) waves are linearly polarized emissions confined near the magnetic equator with wave normal angle near 90° and frequency below the lower hybrid frequency. Such waves, also termed equatorial noise, were traditionally known to be "temporally continuous" in their time-frequency spectrogram. Here we show for the first time that MS wav…
Cold electron heating by EMIC waves in the plasmaspheric plume with observations of the Cluster satellite
Dandouras, Iannis; Yuan, Zhigang; Huang, Shiyong +7 more
We report in situ observations by the Cluster spacecraft of plasmaspheric electron heating in the plasmaspheric plume. Electron heating events were accompanied by enhancements of electromagnetic ion cyclotron (EMIC) waves in the increased density ducts on the negative density gradient side for two substructures of the plasmaspheric plume. Electron…
Observation of double layer in the separatrix region during magnetic reconnection
Zhang, Tielong; Li, Xing; Huang, Can +11 more
We present in situ observation of double layer (DL) and associated electron measurement in the subspin time resolution in the separatrix region during reconnection for the first time. The DL is inferred to propagate away from the X line at a velocity of about ion acoustic speed and the parallel electric field carried by the DL can reach -20 mV/m. …
Waves in a Venus general circulation model
Sugimoto, Norihiko; Takagi, Masahiro; Matsuda, Yoshihisa
Waves in the Venus atmosphere are numerically investigated by extending a work of Sugimoto et al. (2014). Fast superrotating zonal flow of 120 m s-1 at the equator is reproduced and maintained by solar heating for more than 10 Earth years. The meridional distribution of the obtained fast zonal flow is quite consistent with observations …